1 Feb
2011
1 Feb
'11
11:03 a.m.
I was under
the impression that the US mains was in fact 220V (or 230V,
234V, depending on which reference you believe), centre-tapped. The
centre-tap is the 'neutral' wire and is connected to earth ground at one
point. The outside 2 ieres are this 110V with respect to neutral, but as
they're in antipahse there's 220V between them.
Yes, I think that's the basic setup, but as Chuck noted the voltage of one
half is around 120V, not 110V (I got 122.8V on a nearby outlet just now) Most devices are 110V and
run between one live/phase wire and neutral, high-power stuff (cooking
ovens, tumble driers, etc) run their heating elements between the 2
outside wires so as to reduce the current they draw.
As mentioned though, our elderly dryer just runs the elements and the timer
from one 'hot' wire and the motor from the other - perhaps that's
unconventional, though. It does have an interesting effect in that our dryer's
hooked to a load-control setup, but when the power company send a signal to
shut the power to load-controlled devices off (which they do during periods of
peak demand) the dryer stops producing heat and the timer stops advancing, but [1] In the
cases of blocks of flats, student halls of residence, etc,
it's not unheard-of for each floor to be wired to wired to a different
phase. This has led to studend running extension leads to the rooms above
and below theres so as to get a 3 phase supply...
ISTR people doing that in student halls because each room had its own breaker
with a ridiculously-low capacity, so running extensions from other rooms -
sometimes on different floors - was not unheard of. No, if we ant 110V, we have to provide our own
step-down transfoemr
Y'know, I think I remember seeing shaver sockets in UK bathrooms with 120V
outputs (possibly in conjunction with 240V ones; long time since I've seen on
at all). Presumably those had a small step-down inside. from an isolating transformer. Most of thse sockets
have a tapped
secondary winding on the transofemr, and do, indeed, provide 110V as
well.
The trnasofemrs are typically about 20VA, and have many other uses. I
rememebr when a local 'pound shop/ had a load of such sockets, presumbly
bankrupt stock from sowewhere. Yes, I bought quite a few for the
isolating transformers.
-tony